Ground fault protection circuit for multiple loads with separate GFCI branches and a common neutral for the GFCI electronics

ABSTRACT

A ground fault protection circuit for plural loads connected across a power source with plural branches which can be used where the loads are unbalanced. Each branch includes a ground fault circuit interrupter device that has a common line for the electronics of the GFCI separate from the neutral line from the power source to the load where the common lines for the electronics for the ground circuit interrupter devices in each branch are connected to a common point. The ground fault protection circuit employs plural ground fault circuit interrupter devices and eliminates nuisance tripping. The common line for the electronics for a GFCI is routed through the core of the current sensing transformer of the GFCI. The separate neutral line for the electronics, connecting the common lines for the electronics for plural GFCI devices and routing the common lines for the GFCI electronics through the core of the transformer of each GFCI, eliminate improper GFCI operation due to unbalanced loading. The ground fault protection circuit may be used for a three phase power source.

BACKGROUND OF THE INVENTION

1. Field Of The Invention

This invention relates to ground fault protection circuits, and moreparticularly, the invention relates to ground fault protection formultiple loads requiring N Volts across a 2N Volt power source.

2. Description Of The Prior Art

Ground fault circuit interrupter devices are known for detecting aground fault condition and interrupting the flow of current from a powersupply to a load when a ground fault condition is detected. Typically, aground fault circuit interrupter device has two line terminals forreceiving a phase and a neutral line from a power source. Additionally,ground fault circuit interrupter devices include a pair of terminals forconnection to a load. Ground fault circuit interrupter devices include acurrent sensing transformer with a core and a coil wrapped around thecore for sensing a ground fault condition. The ends of the coil of thetransformer are delivered to a sensing circuit which typically includesan amplifier which controls a switching circuit. The switching circuitis connected to the coil of a contactor which opens and closes switchesin the contactor to interrupt the current flowing from the lineterminals to the load terminals in accordance with a signal from thesensing circuit. Further, ground fault circuit interrupter devicestypically include a circuit for powering the ground fault circuitinterrupter device including a full wave rectifier and low voltage powersource. The power circuit provides power to the other electroniccircuits, i.e., the switching circuit and the sensing circuit. Theelectronics derive their power from a connection to the phase lineterminal and the return path is from the electronics to the neutral lineterminal or a ground line.

In certain fields, such as the construction industry, there is a need tosupply power to numerous different loads, such as tools used during theconstruction process. So, for example, there is a need to supply powerto the power saws, power drills, jackhammers, or arc welders. Numerousloads are employed at the same time and are powered from a single powersource. For a 240 Volt power source, a tap of 120 Volts may be employedto power one load, while a second tap of 120 Volts is employed to powera second load. A high current ground fault circuit interrupter devicehas been employed near the power source to provide ground faultprotection to the numerous loads plugged into numerous receptacles of aspider box. Such an arrangement, however, is subject to nuisancetripping from the cumulative effects of leakage current in the numerouspower cords extending from the spider box to the multiple loads. It hasbeen suggested to mount together numerous ground fault circuitinterrupter devices in a spider box where the separate ground faultcircuit interrupter devices are in use at the same time. Thisarrangement would prevent nuisance tripping from affecting the operationof all the loads. Such an arrangement is unsatisfactory, however, due toproblems with unbalanced loading.

When the loads are balanced, with, for example, a 140 Volt load on afirst receptacle and a 140 Volt on a second receptacle, the ground faultcircuit interrupter devices associated with each receptacle will respondto a hazardous condition such as a break in the neutral line. Theneutral line from the power source can be broken or partly severed whenthe spider box is moved around a construction site with rough, rockyterrain or from one construction site to another. The ground faultcircuit interrupter devices associated with the receptacles are intendedto detect any hazardous condition and prevent current being supplied tothe loads are made inoperable.

In fields such as the construction industry, it is frequently the casethat the various loads are not evenly matched. For example, there may bea heavy load with a low impedance plugged into one receptacle and a verylight load (for example, a 25 Volt load) plugged into anotherreceptacle. The entire circuit becomes unbalanced with a low voltage atone receptacle and a high voltage, such as 180-240 Volts at the otherreceptacle. The receptacle with the low voltage load does not providesufficient power to the electronics of the ground fault circuitinterrupter device associated with that receptacle, thereby preventingoperation of that ground fault circuit interrupter device.

There is, therefore, a need for a ground fault protection circuit forplural loads operating from taps from a power source which operatesproperly even when there is unbalanced loading and which is notsusceptible to nuisance tripping.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a ground fault protectioncircuit for plural loads operating off of a power supply that is notsusceptible to nuisance tripping.

A further object of the invention is to provide a ground faultprotection circuit for plural loads operating off of a power supplywhich operates properly even when there is unbalanced loading.

It is a further object of the invention to provide a ground faultcircuit interrupter device that may be connected to a load or pluralloads operating off of a single power supply and that may be connectedto other ground fault circuit interrupter devices in such a manner thatthe ground fault circuit interrupter devices operate even when there isunbalanced loading.

It is still another object of the invention to provide a ground faultcircuit interrupter device which is connected to a load or plural loadsconnected to a single power supply which is not susceptible to nuisancetripping.

Additionally, it is an object of the invention to provide a ground faultcircuit interrupter device that may be connected to a load or pluralloads operating off of a multiple phase power supply and that may beconnected to other ground fault circuit interrupter devices in such amanner that the ground fault circuit interrupter devices operate evenwhen there is unbalanced loading.

These and other objects of the invention are accomplished by providing aground fault protection circuit for multiple loads, each load connectedacross N Volts from a 2N Volt power source comprising n branches, eachbranch supplying power from the power source to at least one of theloads, where n is greater than one; each branch comprising a groundfault interrupter device comprising a first set of terminals forconnection to at least one of the loads; a second set of terminals forconnection across N Volts from the power source; electronics includingmeans for powering the ground fault interrupter device; a common linefor the electronics separate from a neutral line from the power sourceto a load; and a terminal for the common line of the electronics for theground fault interrupter device; and a common connection for theterminals for the common lines of the electronics for each ground faultinterrupter device.

In a preferred embodiment of the invention, a ground fault interrupterdevice comprises a first set of terminals for connection to a load; asecond set of terminals for connection across N Volts of a 2N Voltspower source; electronics including means for powering the ground faultinterrupter device; a common line for the electronics separate from aneutral line from the power source to a load; and a terminal for thecommon line for the electronics for the ground fault interrupter device.

In another embodiment of the invention, a method of providing groundfault protection for multiple loads, each connected across N Volts froma 2N Volt power source comprises providing n branches, each branchsupplying power from the power source to at least one of the loads,where n is greater than one; connecting a ground fault interrupterdevice in each branch between at least one of the loads and the powersource; providing a common line for the electronics of each ground faultinterrupter device separate from a neutral line from the power source tothe load; and connecting the common lines for the electronics of eachground fault interrupter device together.

In a further embodiment of the invention, a method of eliminatingnuisance tripping of a ground fault protection device for plural loads,each connected across N Volts from a 2N Volts power source, comprisesproviding n branches, each branch supplying power from the power sourceto at least one of the loads, where n is greater than one; connecting aground fault interrupter device in each branch between one of the loadsand the power source; and eliminating voltage variations in the powerfor the electronics of the ground fault interrupter devices due tounbalanced loading.

In yet another embodiment, a ground fault protection circuit formultiple loads, each load connected to a phase line of a multiple phasepower source comprises: n branches, each branch supplying power of adifferent phase from the power source to at least one of the loads,where n is greater than one; each branch comprising a ground faultinterrupter device comprising: a first set of terminals for connectionto at least one of the loads; a second set of terminals for connectionacross the power source; electronics, including means for powering theground fault interrupter device; a common line for the electronicsseparate from a neutral line from the power source to a load; and aterminal for the common line of the electronics for the ground faultinterrupter device.

In still another embodiment of the invention, a method of providingground fault protection for multiple loads, each connected to a phaseline of a multiple phase power source comprises providing n branches,each branch supplying a different phase of power from the power sourceto at least one of the loads, where n is greater than one; connecting aground fault interrupter device in each branch between at least one ofthe loads and the power source; providing a common line for electronicsof each ground fault interrupter device separate from a neutral linefrom the power source to a load; and connecting the common lines for theelectronics of each ground fault interrupter device together.

The above and other objects, aspects, features and advantages of theinvention would be more readily apparent from the description of thepreferred embodiment thereof taken in conjunction with the accompanyingdrawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example and not limitation in thefigures of the accompanying drawings in which like reference charactersdenote like and corresponding parts and in which:

FIG. 1 is a schematic diagram of a ground fault protection circuit fortwo loads connected across a 240 Volt power source in accordance with anembodiment of the present invention;

FIG. 2 is a schematic diagram of a ground fault circuit interrupterdevice to be used for each load in the ground fault protection circuitof FIG. 1;

FIG. 3A is a schematic diagram of a ground fault protection circuit forfour loads connected across a 240 Volt power source in accordance withanother embodiment of the invention;

FIG. 3B is a schematic diagram of a ground fault protection circuit forfour loads connected across a 240 Volt power source in accordance withanother embodiment of the invention;

FIG. 4 is a schematic diagram of the ground fault protection circuit ofFIG. 1 illustrating the path of current through the ground fault circuitinterrupter devices; and

FIG. 5 is a schematic diagram of a fault protection circuit for pluralloads connected across a power source for three phases in accordancewith another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a ground fault protection circuit with nbranches for plural loads, each load connected across N Volts from apower source. Referring to FIG. 1, a ground fault protection circuit 10is shown where n is 2 and the power source is a 2N Volt power sourcewhere N is 140 Volts. More particularly, FIG. 1 illustrates anapplication of the present invention with two branches each with a loadand each with a separate ground fault circuit interrupter device 20. Thefirst load is connected across 140 Volts from the 240 Volt power source12. The second load is also connected across 140 Volts from the 240 Voltpower source 12. The 240 Volt power source 12 supplies a first phaseline L1 and a second phase line L2. The voltage between them is 240Volts. The power source 12 further supplies a neutral, central tap whichis the neutral line for the loads. The voltage of the neutral line ishalfway between the first and second phase lines L1 and L2,respectively.

The ground fault protection circuit of FIG. 1 has two branches, onebranch for each of two loads. Each branch includes a ground faultcircuit interrupter device 20 for interrupting power from the powersource 12 to the load when a ground fault condition exists. Each groundfault circuit interrupter device 20 is of the type illustrated in FIG.2. As illustrated, each branch has only one load. However, there may bemore than one load connected to each branch.

As illustrated in FIG. 2, each ground fault circuit interrupter device20 has terminals 14 and 16 for connection to the power source 12 andterminals 22 and 24 for connection to a load. Conductor 26 is the phaseconductor between the phase line terminal 14 and the phase load terminal22. Conductor 28 is the neutral line conductor between the neutral lineterminal 16 and the neutral load terminal 24. Current flowing inconductors 26 and 28 is interrupted when a ground fault condition isdetected in order to eliminate the hazardous condition. Ground faultcircuit interrupter device 20 further has a terminal 30 for the commonline for the electronics of the ground fault circuit interrupter device20. As illustrated in FIGS. 1 and 4, the terminals of the common linesof the electronics of each ground fault circuit interrupter device 20are connected together. Thus, there is a common connection viaconductors 32 and 34 for the common lines for the electronics of eachground fault circuit interrupter device 20.

Referring to FIG. 2, the details of each ground fault circuitinterrupter device 20 are illustrated. Switches 36 and 38 of contactor40 are opened to interrupt the current flow from the line phase andneutral terminals 14 and 16, respectively, to load phase and neutralterminals 22 and 24, respectively, when a ground fault condition isdetected. Current sensing transformer 42 includes a toroidal core 44 anda coil 46 wound around the toroidal core 44 in order to detect a groundfault condition. The ends of the coil 46 of the current sensingtransformer 42 are input to a sensing circuit 48 to detect the groundfault condition. When a ground fault condition is detected, sensingcircuit 48 outputs a signal on line 50 to switching circuit 52 whichpermits current to flow through line 54 and inductor 56. The currentthrough inductor 56 causes the switches 36 and 38 of contactor 40 toopen when a ground fault condition is detected. The electronics 58 ofthe ground fault circuit interrupter device 20 include the sensingcircuit 48, the switching circuit 52 and ground fault circuitinterrupter (GFCI) power circuit 60. GFCI power circuit 60 includes afull wave rectifier and low voltage power source. The GFCI power circuit60 is powered from the line phase line from the power source 12 by aconnection 62 to conductor 26 and the line phase terminal 14. Groundfault circuit interrupter (GFCI) power circuit 60 provides power to thesensing circuit 48 via the conductors 64 and 66, and further, suppliespower to the switching circuit 52 via conductors 68 and 70. The neutralline for the electronics is conductor 72 from GFCI power circuit 60 tothe common terminal 30. The common line 72 may act as a return line andmay be connected to an independent ground point or to the line neutralline 28. The common line 72 for the electronics 58 in the ground faultcircuit interrupter device 20 is routed from the GFCI power circuit 60through the toroidal core 44 of the current sensing transformer 42 tothe common terminal for the electronics 30.

Ground fault circuit interrupter device 20 further may includereceptacles 74 for plugging in additional loads. Thus, each branch mayhave more than one load. As illustrated in FIG. 2, the common 72 linefor the electronics is separate from the neutral conductor 28 betweenthe line neutral terminal 16 and the load neutral terminal 24.

FIG. 4 illustrates the flow of current through two branches of theground fault protection circuit of the present invention. Moreparticularly, as illustrated in FIG. 4, current flows from the powersource 12 along phase line L1 to phase line terminal 14' of GFCI 1. Thecurrent flows from connection 62' to GFCI power circuit 60' to thecommon line for the electronics 72' through the core of the transformerof the GFCI 1 to terminal 30' for the common line of the electronics tothe conductor 32 to the common point 33. The current from line L2 ofpower source 12 passes to the GFCI power source 60" through connectionpoint 62", then along neutral line 72", through the core of the secondtransformer to line 34 to the common point 33. The common point 33 orthe common terminal 30" can be tied to an independent ground point,ground conductor or returned to the line neutral line 28.

In the two GFCI applications of the present invention illustrated inFIGS. 1 and 4, there are two loads and two branches of the ground faultprotection circuit. The voltage of the power source 12 is split evenlybetween the loads 1 and 2. Should the neutral line of the center tapfrom the power source 12 break due to the frequent moving of theportable circuit from one construction site to another, or should theloads be or become unbalanced this will not affect the GFCI powercircuits 60' and 60" which are isolated from the loads 1 and 2,respectively. The GFCI power circuits 60' and 60" do not depend on theload conditions having their own independent common line. Accordingly,the GFCI's will operate properly and hazardous ground fault conditionscan be detected. Further, since each branch of the ground faultprotection circuit has a separate GFCI, leakage current from each powerconductor to each load is not enough to trip the associated GFCI. Thereis no nuisance tripping due to cumulative leakage current for multiplepower conductors to multiple loads sensed by a single high current GFCIfor multiple loads or branches.

FIGS. 3A and B illustrate two different applications of the presentinvention having four branches with four GFCI's. In the ground faultprotection circuits of FIGS. 3A and B, n equals 4 and N equals 140Volts. There are four ground fault circuit interrupter devices 20, eachassociated with a separate load. Half of the loads are connected acrossthe neutral tap of the power source 12 and the first phase line L1 andthe other half of the loads are connected between the neutral tap of thepower source 12 and the second phase line L2. As illustrated in FIG. 3A,the common terminals for the electronics of all of the GFCI's may beconnected to a common point. Alternatively, in the embodiment of FIG. 3Bthe branches for the loads are paired. The common terminals for theelectronics of GFCI power circuits at positions 1 and 3 are connected toa first common point and the GFCI power circuits at positions 2 and 4are connected to a second, independent common point.

Typically the number of branches of loads n is an even number. However,the invention will operate with an odd number of loads and branches. Thecommon terminals for the electronics of the GFCI's are connected to acommon point. The number of branches n may be 2, 4, 6, 8 or any numberthat the power source 12 is able to supply power to.

The present invention may be applied to a three-phase power source 12'.A ground fault protection circuit, in accordance with the presentinvention for a three-phase power source, is illustrated in FIG. 5. Theground fault protection circuit 10' is for multiple loads, for example,Load 1, Load 2, and Load 3. Each load is connected to a different phaseline L1, L2 and L3, respectively, of a multiple phase power source 12'and to the neutral line. There are three branches, each branch suppliespower of a different phase from the power source 12' to one of theloads, Load 1, Load 2, and Load 3. Each branch includes a ground faultinterrupter device 20, as described in detail above, with reference toFIG. 2. Each ground fault interrupter device 20 has a first inputterminal to be connected to one phase line, i.e., L1, L2 or L3, a secondinput terminal to be connected to the power supply 12' neutral line, afirst output to the load phase line, a second output to the load neutralline and separate connections for the GFCI power circuit 60 to the phaseline and to the common point. The terminals for the common lines of theelectronics of each ground fault interrupter device 20 are connectedtogether at a common point 86. Thus, there is a common connection forthe conductors 80, 82, and 84 for the common lines for the electronicsof each ground fault interrupter device 20 located in each branchassociated with each phase of a multiple phase power source 12'. Thecommon line for the electronics of each ground fault interrupter device20 is routed through the core of a current sensing transformer in routebetween the electronics and the terminal 86 for the common lines foreach ground fault interrupter device.

As illustrated in FIG. 5, each branch has only one load. However, theremay be more than one load connected to each branch. A load may beconnected down line from the ground fault interrupter device 20.Further, since each ground fault circuit interrupter device 20 mayinclude receptacles 74 (not shown) for plugging in additional loads,each branch may have more than one load.

In the circuit of FIG. 5, current may flow from the power source 12'along phase line L1 to the phase line terminal of the ground faultcircuit interrupter device 20 GFCI 1. The current flows to the GFCIpower circuit to the common line 80 for the electronics through the coreof the transformer of the ground fault interrupter device 20 to theterminal 86 for the common lines of the electronics. Current flows tothe common point 86 for the common lines for the electronics of theground fault interrupter devices 20. The common point 86, may, as statedabove, be connected to a ground point or connected to the power supply12' neutral line, current flows from phase line L2, through the GFCIpower circuit 60, the transformer core and along line 82 to the commonpoint 86. Similarly current may flow from phase line L3, through theGFCI power circuit, the transformer core and along line 84 to the commonpoint 86. Fewer than three phases may be employed. Alternatively, morethan three phases may be employed depending on the power source.

The present invention provides ground fault protection for plural loads,each load connected across N Volts of a power source by providing nbranches. The number of branches n is greater than one. Each branch mayinclude more than one load. A ground fault interrupter device isconnected in each branch between a load and the power source. A commonline for the electronics of each ground fault interrupter device isseparate from the neutral line from the power source to the load. Thecommon lines for the electronics of each ground fault interrupter deviceare connected together. The common line for each ground faultinterrupter device is routed through the core of the current sensingtransformer for each ground fault interrupter device. Routing the commonline for the electronics through the core of the current sensingtransformer prevents the circuit from tripping on itself since thecircuit accepts current from the phase line from the power source butdoes not supply current to the neutral line of the power source.Providing a common line for the electronics of each ground faultinterrupter device separate from the neutral line from the power sourceto the load and connecting the common lines for each ground faultcircuit interrupter device together eliminates voltage variation for theelectronics of the ground fault interrupter devices due to unbalancedloading.

Each load may be connected across N Volts of a 2N Volt power source.Alternatively, the branches many be for multiple phase lines of amultiple phase power source.

Although the invention has been described with reference to thepreferred embodiments, it would be apparent to one skilled in the artthat variations and modifications are contemplated within the spirit andscope of the invention. The drawings and descriptions of the preferredembodiments are made by way of example rather than to limit the scope ofthe invention, and it is intended to cover within the spirit and scopeof the invention all such changes and modifications.

We claim:
 1. A ground fault protection circuit for multiple loads, eachload connected across N Volts from a 2N Volt power source comprising:a)n branches, each branch supplying power from said power source to atleast one of said loads, where n is greater than one; b) each branchcomprising a ground fault interrupter device comprising:i) a first setof terminals for connection to at least one of said loads; ii) a secondset of terminals for connection across N Volts from said power source;iii) electronics, including means for powering said ground faultinterrupter device; iv) a common line for the electronics separate froma neutral line from the power source to a load; and v) a terminal forthe common line of the electronics for the ground fault interrupterdevice; and c) a common connection for the terminals for the commonlines of the electronics for each ground fault interrupter device. 2.The circuit according to claim 1, wherein each said ground faultinterrupter device further comprises a current sensing transformer witha core; and said common line for the electronics of each ground faultinterrupter device is routed through each said core from the electronicsto the terminal for the neutral line.
 3. The circuit according to claim1, wherein n is an even integer.
 4. The circuit according to claim 1,wherein said power source supplies first and second phase lines with avoltage of 2N Volts between said first and second phase lines and aneutral line at a voltage halfway between said first and second phaselines.
 5. The circuit according to claim 1, wherein each ground faultinterrupter device is connected between one of said phase lines and saidneutral line of said power source.
 6. The circuit according to claim 4,wherein half of n branches are connected between the first phase lineand the neutral line and the other half of the n branches are connectedbetween the second phase line and the neutral line.
 7. The circuitaccording to claim 1, wherein there are n branches for each of threephases of power delivered from said power source.
 8. A method ofproviding ground fault protection for multiple loads, each connectedacross N Volts from a 2N Volt power source comprising:a) providing nbranches, each branch supplying power from said power source to at leastone of said loads, where n is greater than one; b) connecting a groundfault interrupter device in each branch between at least one of saidloads and said power source; c) providing a common line for theelectronics of each ground fault interrupter device separate from aneutral line from said power source to a load; and d) connecting thecommon lines for the electronics of each ground fault interrupter devicetogether.
 9. The method according to claim 8, further comprising:routingthe common line for the electronics through a core of a current sensingtransformer for each ground fault interrupter device.
 10. A method ofeliminating nuisance tripping of a ground fault protection device forplural loads, each connected across N Volts from a 2N Volts powersource, comprising:a) providing n branches, each branch supplying powerfrom said power source to at least one of said loads, where n is greaterthan one; b) connecting a ground fault interrupter device in each branchbetween one of said loads and said power source; and c) eliminatingvoltage variations in power for the electronics of said ground faultinterrupter devices due to unbalanced loading.
 11. The method accordingto claim 10, wherein the step of eliminating voltage variationscomprises:a) providing a common line for the electronics of each groundfault interrupter device separate from a neutral line from the powersource to a load; and b) connecting the common lines for the electronicsof each ground fault interrupter device together.
 12. The method ofclaim 11, further comprising routing the common line for the electronicsthrough a core of a current sensing transformer for each ground faultinterrupter device.
 13. A ground fault interrupter device comprising:a)a first set of terminals for connection to a load; b) a second set ofterminals for connection across N Volts of a power source; c)electronics, including means for powering said ground fault interrupterdevice; d) a common line for said electronics separate from a neutralline from said power source to a load; and e) a terminal for the commonline for the electronics of the ground fault interrupter device.
 14. Theground fault interrupter device according to claim 13, furthercomprising:a) a current sensing transformer with a core; and b) whereinsaid common line for the electronics of the ground fault interrupterdevice is routed through said core from the electronics to the terminalfor the common line of the electronics.
 15. The ground fault interrupterdevice according to claim 13, wherein the second set of terminals is forconnection across N Volts of a 2N Volt power source.
 16. The groundfault interrupter device according to claim 13, wherein the second setof terminals is for connection to one phase of a multiple phase powersource.
 17. A ground fault protection circuit for multiple loads, eachload connected to a phase line of a multiple phase power sourcecomprising:a) n branches, each branch supplying power of a differentphase from said power source to at least one of said loads, where n isgreater than one; b) each branch comprising a ground fault interrupterdevice comprising:i) a first set of terminals for connection to at leastone of said loads; ii) a second set of terminals for connection acrosssaid power source; iii) electronics, including means for powering saidground fault interrupter device; iv) a common line for the electronicsseparate from a neutral line from the power source to a load; and v) aterminal for the common line of the electronics for the ground faultinterrupter device; and c) a common connection for the terminals for thelines of the electronics for each ground fault interrupter device. 18.The circuit according to claim 17, wherein each said ground faultinterrupter device further comprises a current sensing transformer witha core; and said common line for the electronics of each ground faultinterrupter device is routed through each said core from the electronicsto the terminal for the common line.
 19. The circuit according to claim17, wherein there are three phases of power delivered from said powersource.
 20. The circuit according to claim 17, wherein there are nbranches, one branch for each of three phases of power.
 21. A method ofproviding ground fault protection for multiple loads, each connected toa phase line of a multiple phase power source comprising:a) providing nbranches, each branch supplying a different phase of power from saidpower source to at least one of said loads, where n is greater than one;b) connecting a ground fault interrupter device in each branch betweenat least one of said loads and said power source; c) providing a commonline for electronics of each ground fault interrupter device separatefrom a neutral line from said power source to a load; and d) connectingthe common lines for the electronics of each ground fault interrupterdevice together.
 22. The method according to claim 21, furthercomprising:routing the common line for the electronics through a core ofa current sensing transformer for each ground fault interrupter device.